Method and machine for producing a hollow product

ABSTRACT

A method and injection machine for producing a hollow product, such as a urisheath, use of the method for producing a urisheath as well as the urisheath. The machine comprises an annular cavity for receiving a silicone material. The material is injected in a cold state via a coldrun nozzle and cured by heat in the cavity. The cavity has a narrow cross-sectional area over a substantial portion of the cavity and the cavity is connected to a venting area. The cavity has an annular enlarged portion at the proximal portion of the cavity, arranged adjacent said inlet and a groove at the distal portion of the cavity. The narrow cross-sectional area has a decreasing radial dimension towards the distal portion of the cavity. The surface of the cavity is grit blasted.

This is a division of application Ser. No. 12/089,031, filed Oct. 3,2006, the contents of which is hereby incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to a method of producing a hollow,thin-walled product, such as a urisheath, by an injection moldingprocess and an injection molding machine therefore. The invention alsorelates to the use of the injection molding machine for making aurisheath and a urisheath produced by the method.

BACKGROUND OF INVENTION

A urisheath is a product used in urinary catheter devices for aiding inmale urinary incontinence and similar uses. The urisheath comprises acylindrical sleeve enclosing the shaft of the penis and a tip portion towhich a hose may be connected ending in a urine collection bag.

A urisheath is traditionally made by dipping a mandrel with acorresponding design into a latex solution. The dipping process may berepeated several times and the latex is cured between the immersions.

WO 91/17728 discloses a method for manufacturing a urisheath bythermoplastic processing of a thermoplastic material. The tip portion isproduced by injection molding in a tool whereas the thin-walledcylindrical portion is produced integrally with the tip portion by acontrolled extrusion and blow-molding.

WO 2004/004796 discloses a method for producing a urisheath in athermoplastic process for providing a urisheath, which is substantiallyclear to allow inspection of an area of the skin beneath the urisheathwith the urisheath material in contact with the skin. The tip portionmay be produced by injection molding and the cylindrical portion byextrusion, extrusion blow molding, injection blow molding or coldrolling. The tip portion may form an integral part with the cylindricalportion or may be produced as a separate unit, which is subsequentlyconnected with the cylindrical portion. It is also possible to producethe urisheath entirely by extrusion blow-molding.

It is noted that urisheaths made of latex are no longer permitted orsuitable in many countries because of interactions with the skin. Aurisheath made of a thermoplastic material is feasible. However, thethermoplastic material requires addition of plasticizers, which mayinvolve problems in certain cases. A plasticizer can cause migrationproblems, which eventually can cause biological safety issues, and whichalso can cause deterioration of the performance of the skin adhesive onthe urisheaths. A plasticizer can in certain cases also causeenvironmental problems. Urisheaths made of silicone plastic materialsare known in the art. However, such silicone urisheaths are normallymade by dipping a mandrel in a suitable silicone solution, one time orseveral times as mentioned above in connection with latex urisheaths.This process is time-consuming. Moreover, it is difficult to control thewall thickness in such a production method.

Injection molding of silicone materials is previously known from e.g. EP162 037. This patent discloses a method of producing a silicone matt orsilicone domes by injection molding of a silicone material into a cavityhaving a corresponding shape. The material may be a two-componentsilicone material being injected at a low temperature. The cavity andthe form portions may be heated to a high temperature for rapid curingof the silicone material.

In such an injection-molding machine it may be difficult to remove theair when the cavity is filled with material. This problem is addressedin EP 979 718, which discloses suction ports for removing the air.

SUMMARY OF INVENTION

An object of the present invention is to provide a method and a machinefor producing a silicone urisheath or similar product by injectionmolding.

By using an injection-molding machine, the wall thickness of the productmay be controlled very precisely by the design of the cavity of theinjection-molding machine. Thus, a thin-walled product of high qualitycan be produced.

In an aspect of the invention, there is provided a method of producing ahollow product, such as a urisheath, in an injection molding machine,including a mold comprising an annular cavity defined by a core and atleast one side portion, where said cavity has a narrow cross-sectionalarea over a substantial portion of said cavity and said cavity isconnected to a venting area; the method comprising: injecting a siliconematerial into an inlet of said cavity; curing by heating said injectedmaterial in said cavity; opening said mold by moving said at least oneside portion to expose said core with the cured material forming saidproduct; removing said product from said core by grasping one endadjacent said inlet and pulling the product from the core, wherein saidcavity has an annular enlarged portion at the proximal portion of thecavity, arranged adjacent said inlet.

In another aspect of the invention, there is provided a method ofproducing a hollow product, such as a urisheath, in an injection moldingmachine, including a mold comprising an annular cavity defined by a coreand at least one side portion, where said cavity has a narrowcross-sectional area over a substantial portion of said cavity and saidcavity is connected to a venting area; the method comprising: injectinga silicone material into an inlet of said cavity; curing by heating saidinjected material in said cavity; opening said mold by moving said atleast one side portion to expose said core with the cured materialforming said product; removing said product from said core by graspingone end adjacent said inlet and pulling the product from the core,wherein said cavity comprises a groove at the distal portion of thecavity.

In a further aspect of the invention, there is provided a method ofproducing a hollow product, such as a urisheath, in an injection moldingmachine, including a mold comprising an annular cavity defined by a coreand at least one side portion, where said cavity has a narrowcross-sectional area over a substantial portion of said cavity and saidcavity is connected to a venting area; the method comprising: injectinga silicone material into an inlet of said cavity; curing by heating saidinjected material in said cavity; opening said mold by moving said atleast one side portion to expose said core with the cured materialforming said product; removing said product from said core by graspingone end adjacent said inlet and pulling the product from the core,wherein the narrow cross-sectional area has a decreasing radialdimension towards the distal portion of the cavity.

In a still further aspect of the invention, there is provided a methodof producing a hollow product, such as a urisheath, in an injectionmolding machine, including a mold comprising an annular cavity definedby a core and at least one side portion, where said cavity has a narrowcross-sectional area over a substantial portion of said cavity and saidcavity is connected to a venting area; the method comprising: injectinga silicone material into an inlet of said cavity; curing by heating saidinjected material in said cavity; opening said mold by moving said atleast one side portion to expose said core with the cured materialforming said product; removing said product from said core by graspingone end adjacent said inlet and pulling the product from the core,wherein the cavity is blasted.

The silicone material may be injected into said cavity by a coldrunnozzle in a cold state. The material may be injected into said cavityuntil material is received in said venting area. The material may be aliquid silicone elastomer material or a solid silicone material.

In yet another aspect of the invention, there is provided an injectionmolding machine for manufacturing a product, such as a urisheath,comprising: an annular cavity defined by a core and at least one sideportion; a nozzle for feeding a silicone material into an inlet of saidannular cavity; a heating means for heating said core and optionallysaid at least one side portion; opening means for moving said at leastone side portion to expose said core; whereby said cavity has a narrowcross-sectional area over a distal portion of the cavity and the cavityis connected to a venting area, wherein said cavity has an annularenlarged portion at an proximal portion. Said inlet may be arranged atthe top of a proximal portion of said cavity and an annular enlargedportion may be arranged at said inlet for forming a protruding push rimin the product to be formed. The enlarged portion may protrude outwardsin the radial direction.

In yet a further aspect of the invention, there is provided an injectionmolding machine for manufacturing a product, such as a urisheath,comprising: an annular cavity defined by a core and at least one sideportion; a nozzle for feeding a silicone material into an inlet of saidannular cavity; a heating means for heating said core and optionallysaid at least one side portion; opening means for moving said at leastone side portion to expose said core; whereby said cavity has a narrowcross-sectional area over a distal portion of the cavity and the cavityis connected to a venting area, wherein a groove is positioned adjacentsaid venting area for forming a roll rib in the product to be formed.Said groove may be arranged at the end portion of said distal portion ofsaid cavity. Said groove may extend outwards in a radial direction.

In yet still another aspect of the invention, there is provided aninjection molding machine for manufacturing a product, such as aurisheath, comprising: an annular cavity defined by a core and at leastone side portion; a nozzle for feeding a silicone material into an inletof said annular cavity; a heating means for heating said core andoptionally said at least one side portion; opening means for moving saidat least one side portion to expose said core; whereby said cavity has anarrow cross-sectional area over a distal portion of the cavity and thecavity is connected to a venting area, wherein said cross-sectional areahas a decreasing radial dimension towards the distal end of the cavity.

Said venting area may comprise an overflow area and at least one ventingchannel adjacent an end portion of said distal portion for receivingsurplus material injected in said cavity. Said nozzle may be a coldrunnozzle for injecting said material at a temperature of between 5.degree.C. and 50.degree. C., specifically between 15.degree. C. and 40.degree.C., more specifically between 20.degree. C. and 30.degree. C., stillmore specifically about 25.degree. C. Said heating means may be arrangedfor heating said core and optionally said at least one side portion to atemperature of between 80.degree. C. and 200.degree. C., specificallybetween 100.degree. C. and 160.degree. C., more specifically between110.degree. C. and 150.degree. C., still more specifically between135.degree. C. and 145.degree. C.

In a further embodiment, the machine may further comprise removal meansfor removing said product from said core, wherein said removal means maycomprise a sensor device for sensing that the entire product has beenremoved from the core.

In a yet further aspect of the invention, there is provided a use of aninjection-molding machine as mentioned above, for making a urisheathfrom a silicone material.

In a yet still further aspect of the invention, there is provided aurisheath produced by a method as described above. The urisheath may beprovided with a push rim and a roll rib.

BRIEF DESCRIPTION OF DRAWINGS

Further objects, features and advantages of the invention will appearfrom the description of an embodiment of the invention with reference tothe accompanying drawings, in which:

FIG. 1 is a cross-sectional view of an injection-molding tool forproducing a urisheath according to the invention, shown in a closedposition;

FIG. 2 is an enlargement of the injection area;

FIG. 3 is a cross-sectional view similar to FIG. 1, wherein theinjection-molding tool is shown in an opened position;

FIG. 4 is a cross-sectional view similar to FIG. 3 and shows a removingdevice.

FIG. 5 is a side view of a product produced by machine and methodaccording to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 discloses a cross-sectional view of an injection-molding tool formanufacturing a urisheath.

The injection-molding tool 1 comprises a left, movable form section 2and a right, fixed faun section 3. It is mentioned that left and rightand other directions are only in relation to FIG. 1, while the injectionmolding tool may be arranged in any desired direction, vertically asshown in FIG. 1 or 90.degree. or 180.degree. in relation to the positionshown in FIG. 1. The injection-molding tool may alternatively compriseone or several form sections.

Each form section 2, 3 comprise one or several support plates 4, 5 and aheat-insulating plate 6. The support plates 4, 5 and the insulatingplate 6 together support a form plate 7. Form plate 7 comprises a recess8 in which an insertion plate 9 is arranged. The insertion plate 9 isprovided with recesses or shapes that form the outer shape of theproduct to be formed, i.e. the urisheath, or at least a part of theouter shape thereof.

Form section 2 and 3 are designed in a corresponding way, which is notdescribed in detail here other than when there are differences betweenthe form sections 2 and 3.

A core 10 is arranged and shaped for defining the inner dimensions ofthe urisheath.

Form plates 7 of form sections 2, 3 are heated by electrical heaters(not shown), arranged in the form plates 7. Moreover, core 10 is heatedby an electrical heater (not shown) inserted in the center of the core.It is noted that other types of heaters may be used, e.g. hot water oroil under pressure circulating in a duct system in the form plates andthe core.

An injection nozzle 20 is arranged in the fixed form section 3 forinjection of material into a cavity formed between core 10 and the formplates 9 of form sections 2 and 3. The nozzle is arranged at one end ofthe cavity, the proximal end of the proximal portion 15 of the cavity.The injection nozzle may be designed as shown in EP 710 535, thecontents of which is incorporated herein by reference.

The injection nozzle is fixed in the cold support plates 5, 4 of theform section 3 and extends through the insulating plate 6 into the hotregion of form plate 7 of the form section 3.

The injection nozzle 20 comprises a central injection channel 21 havinga diameter of e.g. 2 mm as shown in FIG. 2. Exterior of the injectionchannel there is arranged a cooling jacket 22 enclosing several coolingchannels 27 for a cooling medium such as water. Thus, the injectionchannel is maintained at a low temperature over its entire length. Theinjection channel ends in an injection channel portion 23 with a reduceddiameter. The injection channel with reduced diameter ends slightlybefore an injection opening 24 to a cavity. An end portion 25 of theinjection nozzle is supported by side walls 26 and forms a small cavity29 which is filled by the injection material, which thereby forms a heatinsulation for maintaining the reduced diameter channel portion 23 at alow temperature. Thus, the injection material can be fed to theinjection cavity at a low temperature of e.g. about 25.degree. C. Coldwater is introduced in cooling channels 27 via a supply channel 30. Thenozzle 20 is sealed by several O-ring sealings 28.

The side walls 26 supporting the end portion 25 of the injection nozzlemay be arranged in an insert 31 which is replaceable, so that injectionnozzles having different diameters and shapes may be used in the sameform section by exchanging the insert 31 and the injection nozzle 20.

The proximal portion 15 of the cavity is designed to form the tipportion 52 of the urisheath, shown in FIG. 5, having a relatively largewall thickness. The distal portion 17 of the cavity is designed to formthe cylindrical portion 54 of the urisheath. The cavity has a narrowcross-sectional area, resulting in a cylindrical portion having smallwall thickness. The thickness of the cylindrical portion may beconstant. However, if the cross-sectional area of the cavity has adecreasing radial dimension, resulting in a cylindrical portion having areduced thickness towards the distal end of the cylindrical portion,some advantages are added to the product. A very thin urisheath willprovide increased wearing comfort, as well as it may provide a morebreathable product and thereby increasing the skin friendliness. Alarger thickness in the proximal end of the cylindrical portion preventsthe urisheath from ballooning when in use, and thereby prevents a radialforce on the adhesive, which eventually can loosen the adhesive from theskin and be the cause for a leakage.

The cylindrical portion may have a constant radius or may have certainconicity.

FIG. 1 shows the injection-molding tool in a closed position ready forinjection of material in the cavity. This takes place by feedingmaterial through the injection nozzle 20 to the cavity. The material isinjected into the proximal portion 15 as seen in FIG. 1. The proximalportion corresponds to the tip portion 52 of the ready-made urisheath.The tip portion has the largest wall thickness. Moreover, the proximalend of the proximal portion 15 has an enlarged portion 18, in which theinjected material can be distributed circumferentially around the entireperiphery of the cavity. This ensures that the cavity is filled withmaterial in a uniform manner.

The enlarged portion 18 forms a protruding push rim 51 on the urisheath,shown in FIG. 5. This protruding push rim protrudes outwards in a radialdirection from the tip portion 52. The protruding push rim is usablewhen removing the urisheath from the form. Furthermore, the protrudingpush rim may provide frictional engagement for handling of the productduring use. This is useful when connecting the urisheath to a urine bag.

The push rim may, in an alternative embodiment, extend inwards,completely or partially, i.e. extend both inwards and outwards in theradial direction.

The enlarged portion 18 in the cavity forms an area for receiving thematerial injected into the cavity and distribute the material around theperiphery of the enlarged portion before the material proceeds downwardinto the rest of the cavity. The material then proceeds downwardessentially parallel at all sides of the cavity. Thus, the air in thecavity is expelled more easily and uniformly, which means that the riskof entrapping air inside the cavity is reduced or completely eliminated.

The material proceeds downward inside the cavity and finally reaches thedistal end of the distal portion 17 of the cavity. An overflow area 13is arranged at the distal end of the distal portion of the cavity. Whenthe material reaches the overflow area, some material proceeds out insaid area. In this way, it is assured that the cavity is alwayscompletely filled. Moreover, any air inside the cavity is expelledthrough the overflow area 13. Moreover, the overflow area 13 may beconnected to a space 12 via one or several channels 11 as shown in FIG.3. The cavity ends with a peripheral slit or groove 14, which isconnected to the overflow area 13 over at least a portion. Thus, airinside the cavity is moved downward as seen in FIG. 1 to the groove 14and further to the overflow area 13 and the space 12 via channel 11.Some material will be collected in the groove 14 and further in theoverflow area 13. The material collected in the groove 14 may form anouter roll rib 55 on the urisheath, shown in FIG. 5. The roll rib mayfacilitate the handling of the urisheath after the production process.For the ready-made urisheath the roll rib gives good quality of therolling, without wrinkles, and thus gives good unrolling for the user,and thereby secures a proper attachment on the user without having anywrinkles on the urisheath. This is essential for preventing a leakage.Furthermore, the roll rib may also increase the durability of theurisheath since the thin wall of the cylindrical portion 54 may have lowtear strength and the roll rib may strengthen the distal end portion ofcylindrical portion 54 of the urisheath. The material, which iscollected in the overflow area 13, may simply be removed after thecuring of the urisheath, such as during removal of the urisheath fromthe core.

The overflow area 13 may extend over a portion of the periphery of thecore or insert, such as over almost 180.degree. as shown in FIG. 3, orover a smaller portion, such as 90.degree.

The space 12 may be sufficiently large to accommodate the air that needsto be expelled from the cavity, or may be connected to the atmosphere.

In some embodiments, the overflow area 13 may not be required, but thechannel 11 and the space 12 may accommodate the surplus air.

The material may be a liquid silicone elastomer material, such as aliquid silicone rubber LSR or a solid silicone (HCR, high consistencyrubber).

A silicone elastomer is used because it has a relatively high gaspermeability compared to for example thermoplastics. Moreover, itincludes no phthalates or other organic plasticizers that may be harmfulfor the user or the environment. The material is heat stable and may beautoclaved.

An example of such a material, which may be suitable for use in thepresent invention, is a silicone elastomer No. C6-530 marketed by DowCorning Co. The material is a two-component, platinum-catalyzed liquidsilicone rubber elastomer. The two components are mixed in equalproportions, which are thoroughly blended. The elastomer is thermallycured via an addition-cure, platinum-catalyzed reaction. The resultingelastomer consists of cross-linked dimethyl and methyl-vinyl siloxanecopolymers and reinforcing silica. The elastomer can be used without anypost-cure. The elastomers are heat stable up to 204° C. Airless mixing,metering and dispensing equipment are recommended for productionoperations. Cure of the mixed elastomer is accelerated by heat. Thismaterial has been shown to be particularly suitable for the purpose ofthe present invention.

The material is injected in a cold state by the coldrun nozzle 20. Thetemperature of the material before being injected is between 5° C. and50° C., specifically between 15° C. and 40° C., more specificallybetween 20° C. and 30° C., still more specifically about 25° C.

The form plates surrounding the cavity are heated to a temperature ofbetween 80° C. and 200° C., specifically between 100° C. and 160° C.,more specifically between 110° C. and 150° C., still more specificallybetween 135° C. and 145° C.

The material is injected rapidly into the cavity under high pressure ofmore than 1000 Bar, such as between 1500 to 2200 Bar. At this pressure,the material is a slightly viscous flowing material that can be injectedat room temperature.

Thus, the material fills the cavity in less than a second, such as lessthan a few tenths of a second. The material cures rapidly, in less thanthree seconds. The material is metered by a pump, not shown, so that asufficient quantity is injected to fill the cavity. Alternatively, theinjection can be time operated, so that injection takes place asufficient time period to fill the cavity.

When the material has cured in the cavity, the form is opened as shownin FIGS. 3 and 4. The injection-molded urisheath may be removed bygrasping it at the enlarged tip portion 52 at the top of the core by aremover 40, as shown in FIG. 4. The remover 40 comprises a grip member41 which may grasp the urisheath. The grip member comprises ridges,which interfere with small ribs arranged at the outer surface of the tipportion 52 of the urisheath. The grip member is arranged in a sleeve 42,which is moved down over the urisheath, when the form is opened.Moreover, air under pressure may be injected to make free the urisheathfrom the core and aid in the removal of the urisheath.

The remover pulls the urisheath from the core. Since the urisheath iselastic, it is no problem to withdraw it from the core, although theurisheath includes some portions that have to expand to pass the core,viz. pleated or folded portions in the middle part 53 connecting the tipportion 52 with the cylindrical portion 54 as shown in FIG. 5. Anymaterial extending into the overflow area 13 may be cut off or torn offduring the pulling out of the urisheath.

The cylindrical portion of the urisheath may be rolled before removingthe urisheath from the core, which will make easier the removal of theurisheath from the core.

The remover includes an indication device 42, 43 for indicating that theentire urisheath has been removed and that no material is left in thecavity. This may be accomplished by sensors, such as LED:s and lightsensors arranged to measure the entire length of the urisheath afterremoval from the core. If the urisheath has the expected length over theentire periphery, it is an indication that no material has been left inthe cavity.

The urisheath may be exposed to further treatments after the production,either immediately, or at another site. Such later treatment may be theaddition of an adhesive material and rolling the cylindrical portion.

Any material left in the overflow area 13 is removed, for example byintroducing airflow into the area 13 and the channel/s 11. Thus, theremoval of such material is ensured. This ensures that any material leftfrom the previous injection molding operation, do not interfere with theclosing operation of the form plates and cavity. Then, the cavity isclosed in the opposite order for the next cycle. The injection machinehas several guides for controlling the movement of the form portions sothat no jamming may occur. The mold portions are manufactured with avery high precision so that no or negligible burrs occur in the areas ofintersection between the form portions. Moreover, any residual materialin the injection area should be as small as possible. Thus, theinjection opening is made as small as possible, only some hundredmicrometers.

Because of the shape of the cavity, the material fills the cavity in asmooth and equal manner, so that the cavity may be completely filledbefore any substantial curing has taken place. The material thickness inthe cylindrical portion may be from 0.1 to 0.5 mm, such as 0.15 to 0.30mm, for example, 0.25 mm.

The inner surfaces of the form sections 2, 3 delimiting the cavity maybe surface treated in order to provide a certain roughness of theproduct. Thus, the surface may be grit blasted to level out any sharpsurface irregularities, for preventing that the surface of the productwill be damaged when the product is removed. Moreover, any pores in thecavity surface are closed.

Grit blasting is a mold finishing process in which abrasive particlesare blasted onto the mold surfaces in order to produce a roughenedsurface. The grit may consist of iron, aluminum oxide or any crushed orirregular abrasive.

The blasted surface of the cavity will also provide a certain roughnessof the surface of the ready-made product, which will prevent the productfrom adhering to it or to other products when they are stored or packed.

The insertion plates 9 may be exchanged if a urisheath with anotherdimension should be manufactured.

In order to remove the urisheath from the core, the core can be rotated180.degree. from the position shown in FIG. 4, so that the tip portionfaces downward. For this purpose, pivoting axes may be arranged.

The entire procedure of injection molding the urisheath may take onlyabout 30 to 40 seconds, which is the cycle time. If two or up to eightcores are arranged in parallel in the machine, a high capacity may beobtained. No post-curing is normally required. However, post-curing maybe used for some types of material.

Above, the production of a urisheath has been described. The sameprocedure may be used for producing other types of thin-walled products,such as a balloon or any hollow product having at least one opening. Onesuch exemplifying product is a gastrobelt, which is a type of balloonfor strangling the stomach.

Herein above has been described an injection molding method and machinefor producing a product, such as a urisheath. However, the invention isnot limited to the embodiments disclosed. The different steps can beperformed in other combinations than those identified above. Other meansnormally used within the field of the invention may replace thosedefined above. The invention is only limited by the appended patentclaims.

1. An injection molded urisheath comprising a cylindrical portion havingfirst and second ends, a tip portion disposed at the first end, and apush rim disposed to protrude radially outwardly from the tip portion.2. The urisheath according to claim 1, having an outer roll rib disposedat about the second end of the cylindrical portion.
 3. The urisheathaccording to claim 2, wherein the cylindrical portion has a reducedthickness as the second end is approached.
 4. The urisheath according toclaim 3, wherein the surface of the urisheath is roughened.
 5. Theurisheath according to claim 2, wherein the surface of the urisheath isroughened.
 6. The urisheath according to claim 1, wherein the surface ofthe urisheath is roughened.
 7. An injection molded urisheath comprisinga cylindrical portion having first and second ends, a tip portiondisposed at the first end, and an outer roll rib disposed at about thesecond end of the cylindrical portion.
 8. The urisheath according toclaim 7, wherein the cylindrical portion has a reduced thickness as thesecond end is approached.
 9. An injection molded urisheath comprising acylindrical portion having first and second ends, a tip portion disposedat the first end, and the cylindrical portion has a roughened surface.